1991 Monarch Sliding mirror closet doors-bipass

Judging from the photo, your door could be held together with screws at the side rails of the door. You might want to take your time; I recommend laying the door down on a table or a set of saw horses. That said, if I were you, I would highly recommend contacting a local professional to help you out.

Once you remove the roller, show us a picture, and we'll do our best to narrow down what you need. 

Many thanks for your patience. We carry two similar patio door roller assemblies with steel wheels, one with 1/1/4" diameter wheels, our 81-250, and another with 1/1/2" diameter wheels, our 81-271. We also have a roller with a 1-1/2" diameter nylon wheel, the 23-176. Please compare them to yours as a possible replacement.